Balance wheel structure



March 26, 1940. GRQMANN 2,194,896

BALANCE WHEEL STRUCTURE Filed June 21, 1937 Patented Mar. 26, 1940UNITED STATES PATENT orrlcs 4 Claims.

This invention relates to improved balance wheel structure moreparticularly intended for use with time pieces.

One object of the invention is to provide improved balance wheelstructure wherein the pivot sections or members employed Will be of suchconstructionthat danger of breakage due to severe shocks will be reducedto a minimum.

Another object of the invention is to provide improved balance wheelstructure, the use of which will eliminate a pivot point, one holejewel; and two cap jewels without the loss of precision.

A further object of the invention is to provide structure of thischaracter which, in the event of breakage of any part thereof, may bereadily disassembled so that replacement of the part may be easily made.

The invention seeks, as a still further object, to provide improvedbalance wheel structure which will be simple in construction and easy tomanufacture and which, due to the fact that the parts may be removedwithout difficulty, may be cleaned with the greatest facility.

Other and incidental objects of the invention not mentioned in theforegoing, will become apparent during the course of the followingdescrlption.

My invention is illustrated in the accompanying drawing, wherein:

Figure 1 is a longitudinal sectional view of my improved balance wheelas it would appear properly mounted between the plates of the mountingbracket.

Flgure2 is a horizontal sectional view on the line 2-2 of Figure 1,looking in the direction indicated by the arrows.

Referring now more particularly to the accompanying drawing, whereinlike numerals of reference will be seen to designate similar partsthroughout the various views, the numeral l indicates, in general, amounting bracket of conventional design, including upper and lowersections or plates 2 and 3. It should be understood that anyconventional type of mounting bracket or means may be employed.

My improved balance wheel structure includes a balance wheel which isindicated in general by the numeral 4 and which includes a relativelylarge hub 5 having formed integrally thereon diametrically disposedradial spokes 6 and I. The spokes are of equal length and are disposedin a plane of 180 through the. axis of the wheel. Formed integrally onthe outer end portions of the radial spokes are circumferentiallydisposed balance arms 8 and 9.

As will be seen, the balance armsB and 9 are adapted to have screwedtherein timing screws H]. The timing screws, as best seen in Figure 2,are arrangedon each of the balance arms, in groups, and said groups aredisposed diametrically opposite each other on the arms 8 and 9 and arepreferably arranged in groups of two and three; although at oppositeends of the legs 6 and I there is disposed a single timing screw, thesetiming screws being indicated by the numerals II and I2. As seen inFigure 1 of the drawing, the hub 5 is formed with an integral sleeve I3adapted to have carried thereabout a hair spring ll of conventionalconstruction. The hair spring isadapted to be mounted by a mountingmember l5 carried on an overhanging bracket IS. The overhanging bracketI6, as will be observed, overlies the upper surface of the section 2 ofthe mounting bracket I. It will be seen that the hair spring is simplyand effectively mounted and is so mounted that itwill not [disturb thebalance of my improved balance wheel.

In order to mount the balance wheel, I employ an upper pivot section ormember I! which is threaded through the upper plate 2 and is of uniformdiameter throughout its length. The upper pivot member has a concavelower end surface l8 and said upper pivot member is counterbored axiallyto define a recess l9 which extends upwardly substantially one-third itslength. The upper pivot member is formed with a screw driver slot 20 topermit adjustment. As will be observed, said upper pivot section memberextends freely through the hub 5 and the sleeve 13 thereof so that saidhub and sleeve will not come into contact with the upper pivot memher atany point.

Carried in the lower section or plate 3, in the same axis as the upperpivot member I, is a lower pivot member 2| which is of the same diameteras the pivot member I! and is adapted to be screwed into the plate 3.The lower pivot member has a screw driver slot 22 for permittingadjustment thereof and is provided with an upper end portion 23 whichfits snugly within the recess IS in the upper pivot member. The re ducedupper end portion defines a concave or inwardly inclined shoulder 24 onthe pivot member.

A single jewel 25 is mounted between the concave lower end surface I8and the shoulder 24. The jewel is held in proper position by means of ajewel holder 26-which is held in place on the hub 5 of the wheel 4 bymeans of screws 21. The jewel holder includes a flat circular member 28which cooperates with the hub 5 for holding the jewel in properoperative position. A protecting collar 28a surrounds the jewel. Thejewel holder has fixed thereon the conventional double or single rollerpiece 29 so that said holder will, in efiect, be a combined jewel holderand roller piece.

Adjustment of the balance of said balance wheel may, of course, beeffected by tightening or loosening the timing screws ID in theconventional manner. In view of the fact that the upper and lower pivotsections i1 and 2| are threaded through the plates 2 and 3,respectively, as shown in Fig. l of the drawing, the amount of end shakemay be adjusted to suit the thickness of the jewel 25. It is alsodesired to emphasize that inasmuch as the hub 5 is provided with thesleeve i3, a collar will be defined, which collar will support the hairspring M at its inner end.

Although I have described my improved balance wheel as being primarilyintended for use with time pieces, it should. be understood that thedevice may be used in any instrument where a balance wheel of ordinarytype is employed.

Having thus described the invention, what I claim is:

1. In balance wheel structure, in combination with upper and lowerplates a balance wheel having a hub, a pivot member carried by the lowerplate, a guide member carried by the upper plate and engaging said pivotmember, a jewel rotatably mounted between the confronting ends of themembers, and a jewel holder carried by the hub for securing said jewelto the balance wheel, said jewel providing a single rotatable mountingfor said balance wheel on the pivot member and guide member between theplates.

2. In balance wheel structure as recited in claim 1, wherein the jewelprovides a single rotatable mounting for the balance wheel mediallybetween the plates.

3. In balance wheel structure, upper and lower plates, a pivot membercarried by the lower plate and having a reduced upper end portion, aguide member carried by the upper plate and having a recess at its lowerend to receive the reduced upper end portion of the pivot member, ajewel rotatably mounted on the reduced upper end portion between thepivot member and the guide member, and a balance wheel having a jewelholder for connecting the jewel to said balance wheel, said jewelproviding a single rotatable mounting for the balance wheel.

4. In balance wheel structure, upper and lower plates, a pivot membercarried by the lower plate and having a reduced upper end portiondefining a concave shoulder, a guide member carried by the upper plateand having an axial recess at its lower end receiving the reduced upperend portion of the pivot member, said guide member having a concavelower end surface, a jewel mounted on the reduced upper end portionbetween the circumferential edges defined by the concave surface andconcave shoulder, a balance wheel having a hub surrounding the members,and a jewel holder carried by the hub and cooperating therewith forclamping the jewel to the balance wheel, said jewel providing a singler0- tatable mounting for said balance wheel on the pivot member andguide member, said edges defined by the concave surface and concaveshoulder providing minimum uniform bearing surfaces at each side of thejewel.

FRANCIS C. GROMANN.

